Manipulator for polygonal cross-section billets, particularly cast copper bars

ABSTRACT

The manipulator includes a stationary tipping trough including a pair of longitudinally spaced substantially angular supporting surfaces each having a downwardly and inwardly sloping inlet side and an upwardly and outwardly sloping steeper outlet side. A apir of tipping levers are oscillatable by an associated fluid pressure actuator to engage a longitudinal corner edge of a billet in the tipping trough to tilt the billet so that it rests on a different side. A pair of lifters, having projecting fingers, are oscillatable about the same axis as the tilting levers by a different fluid pressure actuator so that the fingers engage the then lower side of a billet in the tipping trough and move the billet over the outlet sides of the supporting surfaces. The tipping trough preferably is arranged between a billet feeding roller conveyor and a billet discharge roller conveyor, and switch means are provided for engagement with a billet moving along the feeding conveyor. The billets have sloping ends providing respective projecting noses and the switch means are so arranged that, depending upon which switch is engaged by a sloping nose, an appropriate billet tipping operation is initiated. Alternatively, the switch means may be arranged beneath a billet support surface, again for corporation with the nose of a billet, or may be arranged to project into the tilting trough for engagement by the nose of a billet.

United States Patent [1 1 Kreuz et al.

[111 3,759,401 [451 Sept. 18, 1973 MANIPULATOR FOR POLYGONAL CROSS-SECTION BILLETS, PARTICULARLY CAST COPPER BARS [75] Inventors: Otto Kreuz, Duisburg; Stefan Raab,

" Essen, both of Germany [73] Assignee: Demag Aktiengesellschaft, Duisburg,

Germany [22] Filed: June 14, 1971 g 21 Appl. No.: 152,867

[30] Foreign Application Priority Data June 18, 1970 Germany P 20 29 999.4

[52] U.S. Cl 214/1 QG, 198/33 AC [51] Int. Cl. 865g 7/00 [58] Field of Search 214/1 QG, 1 QA, 1 Q,

214/130 R; 198/33 AC, 33 AD [56] References Cited UNITED STATES PATENTS 2,621,805 12/1952 Young ..214/1QG 2,960,240 11/1960 3,182,815 5/1965 DiLeIla et al. 214/1 QG 2,990,512 6/1961 Gewartowski et al. 198/33 R X 3,344,900 10/1967 Drop 193/33 R 2,486,819 11/1949 Brown 214/1 QG X Primary Eraminer- Gerald M. Forlen za Assistant ExaminerFrank E. Werner Attorney-John J. McGlew et al.

57 W ABSTRACT The manipulator includes a stationary tipping trough including a pair of longitudinally spaced substantially angular supporting surfaces each having a downwardly and inwardly sloping inlet side and an upwardly and outwardly sloping steeper outlet side. A apir of tipping levers are oscillatable by an associated fluid pressure actuator to engage a longitudinal corner edge of a billet in the tipping trough to tilt the billet so that it rests on a different side. A pair of lifters, having projecting fin- I gets, are oscillatable about the same axis as the tilting levers by a different fluid pressure actuator so that the fingers engage the then lower side of a billet in the tipping trough and move the billet over the outlet sides of the supporting surfaces. The tipping trough preferably is arranged between a billet feeding roller conveyor and a billet discharge roller conveyor, and switch means are provided for engagement with a billet moving along the feeding conveyor. The billets have sloping ends providing respective projecting noses and the switch means are so arranged that, depending upon which switch is engaged a sloping nose, an appropriate billet tipping operation is initiated. Alternatively, the switch means may be arranged beneath a billet support surface, again for cooperation with the nose of a billet, or may be arranged to project into the tilting trough for engagement by the nose of a billet.

9Claims, l7 Drawing Figures MANIPULATOR FOR POLYGONAL CROSS-SECTION BILLETS, PARTICULARLY CAST COPPER BARS FIELD OF THE INVENTION This invention relates to manipulators for polygonal cross-section billets and, more particularly, to a manipulator which is more compact and is capable of tilting billets for inspection of all surfaces thereof in an efficient and expeditious manner.

BACKGROUND OF THE PRIOR ART Manipulators for oblong workpieces having a polygonal cross-section are known both in rolling mill construction and in testing apparatus for castings in foundries. A manipulator used in rolling mill construction consists of a roller bed with rows of juxtaposed rollers spaced at substantial center-to-center distances from each other and, between these rollers, there are arranged additional rows of rollers spaced at one-half the center-to-center spacing of the first mentioned rollers. As a result, and as viewed in the axial direction of the rollers, tipping troughs are formed, with two rollers, in tandem relation with each other, forming a tipping trough. The rollers are driven and pull the polygonal cross-section workpieces into the trough which tips, due to gravity, into the surface pointing in the direction of workpiece movement. The supporting roller, in this position, is also driven, and moves the workpiece from the trough into the following trough formed by a succeeding roller. The material to be tilted thus is placed successively on all canting surfaces in successive tipping troughs, and thus can be checked by visual inspection. However, this requires an arrangement of several rollers, which in turn results in a relatively long roller bed and thus a very long manipulator. The known device therefore is suitable only in cases where a conveying track is to be connected with the manipulator.

In another known manipulator, a spoke wheel is provided to receive a billet between adjacent spokes. Rotation of the wheel effects a tilting of the billet through 180, so that each billet can be turned over only on the face opposite the preceding bearing surface or face. The turnover remains limited to the initial position. In addition, this device hasthe disadvantage that it is very long, and tilting the workpiece over, in any position, is not possible. Arriving workpieces can be turned over when they have apredetermined position, but a selected number of tilting operations cannot be effected.

SUMMARY OF THE INVENTION The object of the present invention is to improve known manipulators. An improvement meeting all prerequisites requires a compact device which permits turning the polygonal cross-section billet onto all of its sides in succession, or turning with relation to any selected side surface. For stacking copper bars, it is advantageous to place the widest surface of the trapezoidal cross-section on the bottom and, for inspecting the surfaces of billets in rolling mills, it is advantageous to bring all the possible bearing surfaces successively into the range of view of an inspector.

In accordance with the invention, the tipping trough forms at least one stationary substantially angular supporting surface with a preferably flatter or more gently sloping inlet side and a steeper outlet side. One or more canting or tilting levers are pivotally mounted for movement into engagement with a longitudinal corner edge of a billet in the tipping trough to tip the billet. Thus, the tilting levers apply a force to one side of each billet in the trough to rotate the billet about its longitudinal axis, with the swinging movement of a group of tilting levers effecting a turning over of the billet. Since the tilting levers have a low weight, turnovers can be carried out rapidly and in any number. In contrast to known arrangements, there is no feeding movement during the turnover, so that the manipulator can be very short. During the turnover, the polygonal face of the billet then bearing on the trough retains the billet in its new position, so that a turnover can be safely completed with any desired subsequent movement.

The billets positioned in the stationary tipping trough are ready for further movement out of the trough. As a driving means for moving the billets out of the trough, there are provided one or more lifters associated either with the inlet side or the outlet side of the tipping trough, and engaging at least one polygonal surface of each billet. In accordance with another feature of the invention, the drive for moving a billet into the tipping trough and, after turnover, out of the tipping trough, comprises at least one wheel having several projections from its circumference, the wheels being mounted for rotation about an axis which is parallel to the tipping trough.

The positioning of the device embodying the invention is effected very easily for the movement of the billets transversely of thelength of the billet between feeding and discharge roller conveyors. The manipulator thus can be used further in other regions and within 7 different types of foundries or sorting plants. A possible location in a copper bar sorting plant is a position directly after a weighing device from which the copper bars are fed directly into the tipping trough of the manipulator.

For an automatic manipulator, it is desirable to design the tilting lever or levers, moving toward a corner edge of a polygonal billet, so that they can be'swung by an oscillatable drive. Such oscillatable drives can consist of rotary drives or piston drives with pressure being applicable to both sides of the piston. The swinging drive also. can be controlled fully automatically and, to this end, it is proposed to provide a stop in the arriving position of the billets. This stop carries several switches controlling the swinging drive and associated with respective tilted positions of the billets.

In accordance with a further feature, the operations of feeding and discharging billets also can be included in the automatic sequence. To this end, the lifters ex tend above the flatter inlet side, the steeper outlet side, or both of the tilting trough, and each side thereof forms a bearing surface for the billet leading to a respective roller conveyor level, an additional oscillating drive being provided for all the lifters. The lifters can be swung out to disengage them from the billets, and they become operative again only after turning over of a billet.

The turning over of a billet can be effected at random, depending on the position of the arriving billet in a turnover position, which is reached, after a number of turnover operations, by manual control. In accor dance with the invention, there is provided a method for controlling the turnover operation of polygonal cross-section billets. The method is particularly suitable for copper bars which have been produced in a metal mold and which are air-cooled on one surface and have a correspondingly wide base or bearing surface. These wide base surfaces serve to stack a large number of bars, the bars having a generally trapezoidal cross-section. In the stacked position, the weight is stamped on the top side of each bar.

In accordance with the method of the invention, the bars assume such a desired position that their position, when brought to a halt on the feeding roller conveyor in advance of the manipulator, is first determined by actuation of a switch by the billet tip, and this switch actuation initiates, by means of a signal, a corresponding number of oscillations of the swinging drive, after which the swinging drive for the lifters is activated.

An object of the invention is to provide an improved manipulator for polygonal cross-section billets.

Another object of the invention is to provide such a billet in the form of a compact device which permits turning the billet over onto all of its sides in succession, or turning the billet with relation to any one side.

A further object of the invention is to provide such a manipulator including a tipping trough having at least one stationary substantially angular supporting surface with a preferably flatter or more gently sloping inlet side and a steeper outlet side.

For an understanding of the principles of the invention, reference is made to the following description of typical embodiments thereof as illustrated in the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING In the Drawing:

FIG. 1 is a side elevation view of a manipulator embodying the invention;

FIG. 2 is a top plan view of the manipulator shown in FIG. 1;

FIG. 3 is a sectional view taken on the line AA of FIG. 2, in part, and in part an enlarged front elevation view corresponding to FIG. 2;

FIGS. 4, 6, 8 and are elevation views, taken in a viewing direction along a roller conveyor, illustrating various phases of the switching procedures initiated by arriving billets;

FIGS. 5, 7, 9 and 11 are side elevation views corresponding, respectively, to FIGS. 4, 6, 8 and 10;

FIGS. l2, l3 and 14 are elevation views illustrating another embodiment of a control switch and its method of operation; and

FIGS. 15, 16 and 17 are elevation views illustrating still another embodiment of a control switch and its manner of actuation by billets.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The manipulator illustrated in FIG. 1 is representative of an application of the invention to an inspection station arranged behind or following a copper bar foundry. In itself, the manipulator thereforeneed not be used only in connection with additional conveyor means, but it can also be used separately and the billets do not have to consist solely of metal.

Referring to FIGS. 1, 2 and 3, a frame 1 is supported on legs 2 and 3, and the material to be turned comprises billets 4. By means of parts described hereinafter, a single billet 4 arrives in tipping trough 5, which consists of two supporting surfaces 6 and 7 arranged at an angle to each other. Supporting surface 6, which is the inlet side, is less steep than supporting surface 7, which is the trough outlet side. The illustrated billet 4 has a trapezoidal cross-section, and thus has four longitudinally extending corner edges 8.

As best seen in FIG. 2, two supporting surfaces 6 and two supporting surfaces 7 are arranged along the length of a billet 4. Each supporting surface 7 extends as an arc and forms, toward the discharge side of the trough, a bearing surface 9. Supporting surfaces 6 and 7 are so narrow that they essentially form rails. As a result, there is sufficient room to provide tilting or canting levers 10 between each pair of supporting surfaces 6, 7, and tilting levers 10 are secured to a tubular shaft 11.

Lifters 12 are provided and arranged for swinging or oscillation independently of shaft 11, each lifter 12 comprising projections arranged around the periphery or circumference of a respective wheel 13. Wheels 13 can be turned about the same axle 14 which rotatably supports shaft 11.

Tipping trough 5 is arranged between a feeding roller conveyor 15 and a discharging roller conveyor 16. The rollers 17 of the respective conveyors form conveying planes 18, as best seen in FIG. 1, along which billets 4 can be conveyed in dependence on the direction of motion of the driven rollers 17. FIG. 2 illustrates the billet feeding device 19 and the billet discharging device 20.

The pair of tilting levers 10 secured on shaft 11 can be actuated by an oscillating drive 21. For this purpose, shaft 11 has secured thereto a lever 22 whose free end is articulated, at a joint 23, to the connecting rod of a hydraulically actuated piston-cylinder drive 24. Drive 24 is, in turn, connected with supporting frame 1 through an articulation at a housing 25.

Movement of a billet 4 in the direction 19 is limited by a stop 26, in which there are arranged switches 27, 28 and 29 for actuating the oscillating drive 21, with the method of operation of these switches being explained hereinafter.

Shaft 11 is tubular or hollow and has, at both ends in its interior, bearings 31 by means of which it is rotatably supported on shaft 30. As best seen in FIGS. 2 and 3, shaft 30 carries the spaced wheels 13 which are secured to rotate with shaft 30 by keys 32. In correspondence with the lengths of billets 4, wheels 13 are arranged between bearings 33 which are fixedly mounted on supporting frame 1. Outwardly of bearings 33,.

ratchets 35a are fixed to shaft 30 torotate therewith, and respective pairs of levers 35 are oscillatably mounted on the hubs of each ratchet 35a. The ends of levers 35 support pivot bolts 36, with one pivot bolt mounting a pawl 37 engageable with the associated ratchet 35a. The other pivot bolt connects the associated pair of levers to the piston rod of a piston-cylinder drive 38. The piston-cylinder drives, or linear fluid pressure actuators, 24 and 38 can be controlled independently of each other. By virtue of their pivotal interconnection with the associated levers 35 through bolts 36, drives 38 can be positioned on either side of the tilting trough. In the illustrated embodiment, the drives 38 are arranged adjacent feed roller conveyor 15.

The rollers 17 of feed roller conveyor 15, which are driven by means of chains and sprockets, move billets 4 toward stop 26. As illustrated in FIGS. 4 and 5, they billet has the form of a copper bar, and such copper bars have tips 40. If billet 4 therefore rests on its base 41, which is characteristic of a trapezoidal crosssection, nose 40 will actuate switch 29. Switch 29 transmovement is always one complete reciprocation of the piston rod of drive 21.

In the phase illustrated in FIGS. 6 and 7, billet 4 rests on its side face 42, and its nose 40 consequently actu ates switch 28, with switches 27 and 29 remaining inactive. Switch 28 is set, for controlling drive 21, in such a way that a single pulse is emitted. Billet 4 is thus tilted to rest on its base 41 and is advanced in this position. Further movement of the billet 4 is then effected, on the basis of the last pulse supplied to drive 21, by pivot drive 28 oscillating lifters 12 which push billet 4 along trough outlet surfaces 7 and bearing surfaces 9 onto discharge roller conveyors 16. As stated, the last billet tilting pulse initiates operation of drive 38 for lifters 12.

In the phase shown in FIGS. 8 and 9, billet 4 rests on its upper or head surface 43, so that its tip 40 actuates switch 27. This initiates two tilting cycles effected by drive 21, after which there follows the actuation of drive 38 for lifters 12 to discharge the billet from the tilting trough.

The phase shown in FIGS. 10 and 11 is similar to that in FIGS. 6 and 7, so the switch 28 again is actuated by tip 40 of billet 4 which is now resting on its side face 44. The same billet tilting and discharge procedures occur as described above.

As shown in FIGS. 12, 13 and 14, other switching means may be provided either to inspect the billet re: peatedly, after a determinable number of pulses for tilting operations, or to discharge it in a selected orientation. To this end, there is provided at least one lever 45 pivoted intermediate its ends on an axle 46 in supporting frame 1. Each pivot lever 45 has a tip 47 which extends by a certain amount above inlet side 6 of trough 5 and inwardly of inlet side 7 of trough 5. Depending on the orientation of a billet 4, having a tip 40, the tip 47 of lever 45 is engaged by the billet. In FIG. 12, there is no contact between the billet and the lever.45, so that there is no movement of the lower end 48 of each lever. Consequently, the actuator 49 of switch 50 remains in the rest position. In FIG. 13, billet 4 has its upper or head face 43 toward the upper end of lever 45, so again there is no pivoting of lever 45 due to the bevel 51 at the tip of the billet. This bevel is more clearly illustrated in FIG. 15.

In FIG. 14, however, the base 41 of billet 4 faces outlet side 7 of the trough and, as billet 4 is notbevelled on its base, as is the case for the surfaces 51 of FIG. 16,

pivot lever 45 is turned by a certain amount corresponding to the projection of the tip 47. Thus, the rear or lower end of lever 45 operates actuator 49 to actuate switch 50. The pulses provided by switch 50 can be transmitted in the same manner as described to drive 21, drive 38, or both.

FIGS. 15,16 and 17 illustrate a further control switch 52 which, instead of an operating lever 49, has a reciprocable operating pin 53 but otherwise works in a manner similar to the principle illustrated in FIGS. 12, 13. and 14. In FIG. 15, billet 4 rests on its side face 42, and

thus does not touch pin 53 with its tip 40 or, respectively, the surfaces 51. The same holds true for the phase illustrated in FIG. 16. In FIG. 17, however, billet 4 rests on its base 41, and its tip 40 therefore actuates roller conveyor 15 or by an easily constructed sloping trough, which has not been shown, along which the billets 4 move by gravity. In connection with feed roller conveyor 15, it is advisable to provide a sliding mover 54, as shown in FIG. 2, which moves billet 4 transversely of the roller conveyors in the rhythm of the op.- eration of the manipulator, through the medium of a linear actuator of the piston-cylinder type 55. Movement of slide 55 can also be initiated by switches 15 or 52.

While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.

What is claimed is: p I

1. 'In a manipulator-for polygonal cross-section billets, particularly cast copper bars, having a tipping trough for tilting of the billets andmeans for feeding the billets to the tipping trough and for receiving billets from the tipping trough: the improvement comprising, in combination, a single tipping trough having at least one pair of stationary angularly related supporting surfaces intersecting at substantially right angles to each other to form a substantially V;-shaped apex andeach forming an uninterrupted stablesupporting surface for billets movedsidewise into and out of said trough; one of. said surfaces sloping upwardly and outwardly from said apex at a relatively small angle and normally serving as a billetreceiving side of said trough; the other surface sloping upwardly and outwardly from said apex at a steeper angle and normally serving as a billet discharging side of said trough; each polygonal crossside surface of the billet into stably supported relation with the stable supporting surface previously engaged by said one side surface;said tipping lever being repetitively oscillatable to tilt the billet an'unlimited number of times to bring selected side surfaces of the billetinto stably supported relation with the stable supporting surface initially engaged by said one side surface of the v billet.

2. In a manipulator for polygonal cross-section billets, the improvement claimed in claim 1,including at least one billet lifter engageable with at least one side surface of a billet in said trough to discharge the billet along a respective one of said uninterrupted stably supporting surfaces of said trough; each lifter being associated with one of the sides of said trough.

3. In a manipulator for polygonal cross-section billets, the improvement claimed in claim 2, in which each lifter comprises a wheel having plural projections extending from its circumference; and means mounting each wheel for rotation about an axis extending parallel to said tipping trough.

4. In a manipulator for polygonal cross-section billets, the improvement claimed in claim 1, in which said tipping trough is positioned between two substantially parallel feeding and discharging roller conveyors for transferring billets, in a direction transverse to the billet length, between the two conveyors.

5. In a manipulator for polygonal cross-section billets, the improvement claimed in claim 1, including a drive connected to each tipping lever and operable to oscillate the same.

6. In a manipulator for polygonal cross-section billets, particularly cast copper bars, having a tipping trough and driving means for feeding the billets through the tipping trough, the improvement comprising, in combination, said tipping trough having at least one stationary substantially angular supporting surface with a sloping inlet side and a steeper outlet side; at least one pivotal tipping lever pivotal in engagement with a longitudinal corner edge of a billet in the tipping trough to tilt the billet; a drive connectedto each tipping lever and operable to oscillate the same; a stop engageable by a billet arriving adjacent said tipping trough; and at least one switch on said stop engageable by an arriving billet and controlling operation of said drive for oscillating each tipping lever; each switch effecting an operation of said drive in accordance with the respective orientation of the arriving billet.

7. In a manipulator for polygonal cross-section billets, the improvement claimed in claim 6, in which there are plural switches on said stop each engageable by an. arriving billet in accordance with a respective orientation of the arriving billet, and each efiecting a respective operation of said drive effective to tip the billet so that it rests on a predetermined side surface.

8. In a manipulator for polygonal cross-section billets, the improvement claimed in claim 4, in which the projections of each lifter are movable upwardly past the inlet side of said trough; each side of said trough constituting a bearing surface connecting the trough to a respective roller conveyor at the transport level of the associated roller conveyor.

9. In a manipulator for polygonal cross-section billets, the improvement claimed in claim 4, in which the projections of each lifter are movable upwardly of the steeper outlet side of said trough; each side of said trough forming a bearing surface connecting the trough to a respective roller conveyor at the transport level of the associated roller conveyor. 

1. In a manipulator for polygonal cross-section billets, particularly cast copper bars, having a tipping trough for tilting of the billets and means for feeding the billets to the tipping trough and for receiving billets from the tipping trough: the improvement comprising, in combination, a single tipping trough having at least one pair of stationary angularly related supporting surfaces intersecting at substantially right angles to each other to form a substantially V-shaped apex and each forming an uninterrupted stable supporting surface for billets moved sidewise into and out of said trough; one of said surfaces sloping upwardly and outwardly from said apex at a relatively small angle and normally serving as a billet receiving side of said trough; the other surface sloping upwardly and outwardly from said apex at a steeper angle and normally serving as a billet discharging side of said trough; each polygonal crosssection billet, when moved sidewise into said trough, abutting one of said stable supporting surfaces and having one side surface thereof stably supported on the other of said stable supporting surfaces; and at least one tipping lever pivotally supported in said manipulator adjacent said tipping trough and having a free end engageable with a longitudinal corner edge of a polygonal cross-section billet then in said tipping trough to tilt the billet about its longitudinal axis to bring a different side surface of the billet into stably supported relation with the stable supporting surface previously engaged by said one side surface; said tipping lever being repetitively oscillatable to tilt the billet an unlimited number of times to bring selected side surfaces of the billet into stably supported relation with the stable supporting surface initially engaged by said one side surface of the billet.
 2. In a manipulator for polygonal cross-section billets, the improvement claimed in claim 1, including at least one billet lifter engageable with at least one side surface of a billet in said trough to discharge the billet along a respective one of said uninterrupted stably supporting surfaces of said trough; each lifter being associated with one of the sides of said trough.
 3. In a manipulator for polygonal cross-section billets, the improvement claimed in claim 2, in which each lifter comprises a wheel having plural projections extending from its circumference; and means mounting each wheel for rotation about an axis extending parallel to said tipping trough.
 4. In a manipulator for polygonal cross-section billets, the improvement claimed in claim 1, in which said tipping trough is positioned between two substantially parallel feeding and discharging roller conveyors for transferring billets, in a direction transverse to the billet length, between the two conveyors.
 5. In a manipulator for polygonal cross-section billets, the improvement claimed in claim 1, including a drive connected to each tipping lever and operable to oscillate the same.
 6. In a manipulator for polygonal cross-section billets, particularly cast copper bars, having a tipping trough and driving means for feeding the billets through the tipping trough, the improvement comprising, in combination, said tipping trough having at least one stationary substantially angular supporting surface with a sloping inlet side and a steeper outlet side; at least one pivotal tipping lever pivotal in engagement with a longitudinal corner edge of a billet in the tipping trough to tilt the billet; a drive connected to eacH tipping lever and operable to oscillate the same; a stop engageable by a billet arriving adjacent said tipping trough; and at least one switch on said stop engageable by an arriving billet and controlling operation of said drive for oscillating each tipping lever; each switch effecting an operation of said drive in accordance with the respective orientation of the arriving billet.
 7. In a manipulator for polygonal cross-section billets, the improvement claimed in claim 6, in which there are plural switches on said stop each engageable by an arriving billet in accordance with a respective orientation of the arriving billet, and each effecting a respective operation of said drive effective to tip the billet so that it rests on a predetermined side surface.
 8. In a manipulator for polygonal cross-section billets, the improvement claimed in claim 4, in which the projections of each lifter are movable upwardly past the inlet side of said trough; each side of said trough constituting a bearing surface connecting the trough to a respective roller conveyor at the transport level of the associated roller conveyor.
 9. In a manipulator for polygonal cross-section billets, the improvement claimed in claim 4, in which the projections of each lifter are movable upwardly of the steeper outlet side of said trough; each side of said trough forming a bearing surface connecting the trough to a respective roller conveyor at the transport level of the associated roller conveyor. 